Research on the reasons of red water in a southern city in China
南方某城市供水管网红水原因调查与研究

The red water in the drinking distribution systems of a southern city was investigated by analyzing the water quality, such as DO, residual chlorine, iron, manganese, iron bacteria and ammonia-oxidizing bacteria. The objectives of this study were to identify the reasons of red water with the aim to supply the answer to this problem. The results showed that the main compositions of the deposits were iron and manganese. There were manganese overstep (the maximum of Mn could reach to 0.33 mg·L-1) in the plant effluent with Larson ratios>1 and the significant difference in water quantity, sulfate and electrical conductivity among the four plants. The density of the iron bacteria and ammonia-oxidizing bacteria (100 -103 MPN·mL-1) was high. The potential reason for the red water was the water corrosion of plant effluent. Secondly, the red water easily occurred in the distribution systems with lower DO and residual chlorine. In addition, serious nitrification caused microbiological corrosion was another vital reason. According to the research, the primary methods for controlling red water were proposed.